Supermarket Tesco will be the first major high street retailer to sell fresh octopus and cuttlefish, as part of an expanded range of "alternative" varieties of fish and seafood which it says is in response to soaring demand from environmentally minded shoppers.

Its selection of seasonal fresh fish rises by a third this week from 40 to 60 varieties. Among the new, sustainably caught seasonal lines being added to its fresh fish counters are fresh octopus, squid and dover sole. Other new lines which will be sold as they become available include witch soles (known as 'poor man's dover sole), black bream, cuttlefish and anchovies. All of the new fish varieties will be caught in and around British coastal waters, particularly in the south-west of England.

Tesco's Catch of the Day range is the latest move by retailers and marine conversation groups to encourage more consumers to buy sustainable fish. Five species – cod, haddock, salmon, tuna and prawns – make up 75% of UK consumption.

The cook and Guardian writer Hugh Fearnley-Whittingstall last year led the Fish Fight campaign backed by chefs such as Jamie Oliver, which aimed to encourage consumers to reduce over-fishing by switching to less popular but sustainable fish.

Tesco fish specialist Gary Hooper said: "We aim to offer customers far more choice than they've had before so that they can buy alternatives to the big five species – and help take pressure off endangered species. Last year, we launched a training programme for our fish counter staff in order to encourage and advise customers about trying new species of fish which has already proved a great success. We think that, given more choice and encouragement such as preparation and cooking advice, many shoppers will be ready to try something new. This move will also benefit British fishing fleets."

Tesco's campaign to encourage shoppers to try new fish varieties is already showing strong results. In the pat year, the supermarket reports that sales of lemon sole fillets are up by 400% and dyed kippers up by 259%.